Japanese Patent Application Publication No. S62-14675 discloses a fixing device including a heater, a pressure belt providing a nip region in cooperation with the heater, and two rollers supporting an inner peripheral surface of the pressure belt. The pressure belt is nipped between the heater and each of the two rollers, which are disposed at an entry position and an exit position of sheets. Therefore, an enlarged nipping region can be provided, and contacting width between the sheet and the heater can be increased, whereupon enhanced heating efficiency can be obtained.